Field of the Invention
The present invention relates to seawater desalination devices and seawater desalination methods based on an evaporation method. In particular, the present invention relates to a seawater desalination device and a seawater desalination method based on an evaporation method, which are effective for stable water supply without causing water shortage issues. In addition, the present invention relates to a seawater desalination device and a seawater desalination method based on an evaporation method, which are suitable for salt production.
Description of the Related Art
An evaporation method and a membrane method are available for seawater desalination.
Such an “evaporation method” includes a multi-stage flash method and a multiple effect method. On the other hand, such a “membrane method” includes a reverse osmosis membrane method and an electrodialysis method.
When desalinating seawater using such an “evaporation method” described above, water can be obtained with an advantageously lowered salinity concentration. However, a large amount of energy is disadvantageously required throughout a desalination process of the method. In addition, when seawater is concentrated to a high level for desalination through the “evaporation method” described above, some phenomena including scaling can occur in a device and other equipment, resulting in some problems including lowered thermal efficiency.
Such scaling and other phenomena occurred through a process of an evaporation method further can cause sulfate and carbonate to be extracted from scaling components such as calcium and magnesium in seawater due to concentration and raised water temperature, and to be adhered onto a surface of a heat transfer pipe. Because of this, thermal transfer efficiency is disadvantageously lowered, thus an amount of produced water is reduced. (Issued in Special edition/The basics and applications of water treatment technologies/The latest trends of seawater desalination, Chemical Devices, vol. 51(8), pp. 25-30, 2009-08-00 Kogyo Chosakai Publishing Co., Ltd.)
Advantageously, desalinating seawater based on the “membrane method” described above consumes less energy, when compared with the evaporation method described above. However, any pretreatments including sterilization and removal of adhering matters are required. In addition, because the obtained water has a high level of salinity concentration, the water can neither be used for industrial water nor city water.
JP-A-2010-36056 describes a “heating module” that includes a “first heat exchanger” for exchanging heat between an input fluid and an output fluid; a “first compressor” for compressing and heating either of the input fluid or the output fluid; and an expansion machine for expanding and cooling the input fluid. The “heating module” described in JP-A-2010-36056 has an object to increase an energy saving effect.
JP-A-2010-36057 describes a “separation process module” that includes a “separator” for separating an input fluid that includes a first component and a second component into a first output fluid that includes the first component and a second output fluid that includes the second component; and a “first compressor” for compressing and heating the first output fluid output from the separator. In addition, the “separation process module” described above includes a first heat exchanger, a second heat exchanger, and a third heat exchanger. The “separation process module” described in JP-A-2010-36057 has an object to increase an energy saving effect.
The modules described in the aforementioned conventional art can be appreciated in the view point of increasing energy efficiency. However, the modules are not suited for seawater desalination. For example, the modules described in the aforementioned conventional art are difficult to recover and treat obtained “liquids” such as a desalinated liquid and extracted “solids” such as salt both obtained when desalinating seawater.
In addition, because the modules described in the aforementioned conventional art are difficult to recover and treat obtained “liquids” such as a desalinated liquid and extracted “solids” such as salt, these modules are also difficult to solve problems including a reduced amount of produced water due to lowered thermal transfer efficiency caused by sulfate and carbonate extracted from calcium and magnesium through concentration and raised water temperature and adhered onto a surface of a heat transfer pipe.
Embodiments of the invention have been made in view of solving the above-mentioned problems, and therefore provide a seawater desalination device and a seawater desalination method based on an evaporation method, which can reduce, by using an self-heat recuperation process, an amount of necessary energy in half or less, compared with a conventional multi-stage flash method. Particularly, embodiments of the invention are aimed to provide a seawater desalination device and a seawater desalination method based on an evaporation method through which, by using a three-phase fluidized bed, a high thermal efficiency operation is possible even at a high salinity concentration level, while preventing scaling to a heat-transmitting surface.